Objective:This study was to investigate the variables in bone marrow harvesting procedure and individual donor factors which can potentially affect the yield of mesenchymal stromal cells(MSC).Methods:We determined the yield of MSC from bone marrow under different clinical conditions by comparing the MSC colony numbers from:(1) donors of different ages;(2) healthy donors and patients with leukemia;(3) bone marrow aspirated at different time points during marrow harvesting;(4) bone marrow harvested by different needles.Results:During the process of harvesting,the number of MSC significantly decreased with increase number of aspiration,from 675/ml at the initial decreased to 60/ml after 100 ml bone marrow aspirated,and 50/ml after 200 ml bone marrow aspirated.The number of MSC retrieved from leukemia patients(99/ml bone marrow) was significantly lower than that of healthy donors(708/ml bone marrow).However,there was no significant difference in growth rate.There was no significant age-related difference of MSC yielded from donors <55 years.And there was no significant difference in MSC number between the samples from single end-holed needle and those from multiple-side-hole needle.Conclusion:The optimal bone marrow samples for MSC collection should be obtained earlier in the process of harvesting procedure.Bone marrow from donors <55 years was equally good as MSC sources.The autologous MSC from leukemia patients can be utilized for in-vitro MSC expansion. Objective: This study was to investigate the variables in bone marrow harvesting procedure and individual donor factors which could potentially affect the yield of mesenchymal stromal cells (MSC). Methods: We determined the yield of MSC from bone marrow under different clinical conditions by comparing the MSC colony numbers from: (1) donors of different ages; (2) healthy donors and patients with leukemia; (3) bone marrow aspirated at different time points during marrow harvesting; (4) bone marrow harvested by different needles. Results: During the process of harvesting, the number of MSC significantly decreased with increase number of aspiration, from 675 / ml at the initial decreased to 60 / ml after 100 ml bone marrow aspirated, and 50 / ml after 200 ml bone marrow aspirated. MSC retrieved from leukemia patients (99 / ml bone marrow) was significantly lower than that of healthy donors (708 / ml bone marrow). There was no significant difference in growth rate. Here was no significant age-rel ated difference of MSC yielded from donors <55 years. Again there was no significant difference in MSC number between the samples from single end-holed needle and those from multiple-side-hole needle. Conlusion: The optimal bone marrow samples for MSC collection should be obtained earlier in the process of harvesting procedure. Bone marrow from donors <55 years was equally good as MSC sources. The autologous MSCs from leukemia patients can be utilized for in vitro MSC expansion.